Gas distribution means



Feb. 10, 1959 T. M. GILBERT 2,873,180

GAS DISTRIBUTION MEANS Original Fil ed Nov. 12, 1953 2 Sheets-Sheet 1 Fig. .1.

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' zsratss Patented Feb. 110, 1195i .Cutler-jliammer, lino, Milwaukee, Wis, a leorporatiau oilleiaware .Continuationof application Serial No. 391,483, November 12,11953. .This applicationMarsh 14, 1957,;Serial Not 646,172

2 Claims. (Ci. dbl- W2) This invention relates -to improvements in'means .for supplying gas to gas distribution systems.

This .is a continuing application of my application Serial "No. 391,483, filed November 12, 1953, now abandoned.

Modern gas .supply systems frequently :requirelgasto be distributed at both low and intermediate pressures. Inasmuchas the .peak demands iforgas .iniboth the low pressure and intermediate pressure systems often exceed the rate :atwhich the gas is supplied from its source, gas storage equipment mustbe provided. It has been customary, in \such systems, to provide means to store some gas :at low pressure to be released directly into the low pressure distribution system and toprovide meansto store atquan- -tity.-of the l gas at high :pressure .to be released :to the intermediate pressure .distribution'system through a suitable pressure regulator.

However, the quantity of gas which canzbe supplied etc the intermediate distribution system from the high pressure storage equipment limited by "the capacity of the latter-so that a very large and expensive high pressure gas holder is usually required. Moreover, a large amount ofenergy, which :is costly 110 provide and .most of which is not recovered, is expended in pumping gas into the high pressure holder. i

Accordingly, a :primary object ,of :the .invention is to .provide {improved means for distributing gas.

Another object is :to provide means .for distributing gas .efliciently and at unusually low cost. Another object is to :provide improved .means whereby the ratio of the quantity of gas supplied to an inter- .mediate pressure system to the quantity of gas stored at high pressure is increased.

Other objects and advantages ,of the invention will -hc ei.r atte app r I 1? a c mp ying drawings illustrate ;an embodiment ofthe invention in the form of a distribution system of a public utility gas company, it being understood that other embodiments o f the invention ,are possible Withoutdeparting from the-scopeof ttheappended claims. In the draw 1Fig. .1 schematically shows a gas distribution system constructed in .accordancewith the present inventiQn; and Fig. 2 is a partly schematic and partly diagrammatic illustration of anintermediate pressure pump .and regulator employed in the system'ofFig. 1.

Referring to Big. .1, the system comprisesa low .pressure storage tank or holder ,LP, a high pressure stolagfi tanker holder HP, a pump 1P, a low pressure distribution system LPS, and an intermediate pressure .distribution system IPS, The system further comprises a high pressure pump P, a regulating valve VR and a check ,valve VCF.

The pump IP represents a unit of any type which can utilize the energy stored in compressed gas to pump the lo pre r gas. I Preferab y. but. not necessarily, comprises multiple rate compressors; which preferably are of the jet compression type. It may comprise,

fforwexample a multiple rate jet compressor of the :type "hereinafter described :in connection withTl-iig. 2 and disclosed in United States Patent No. 2,637,638, granted :MayS, 1953, toEdwin X. Schmidt, as assignee of Cutler- -Hammer, Inc. The character R designates .a conitrollenor'regulator:for pump IP, also shown in .therightth'andiportion tofliig. 2. 7

Gas 11's delivered from .a suitable source through a conduit t l at low .pressure to holder *LP where it is stored. :S'orne ofthe gas ,is permittedto flow to the low pressure distributionssystem LPSthroughconduits 2 and 2a. Other gaswhich .fiowsxfrom holder LP through 'conduits 2 and 3=to:-p ump ;P, is pumped by the latterthroughconduit 3a do lhigh pressure :tankl-IP where it is stored at high pressure.

ZCOIldlJllS =4 (and .6 connect the high pressure holder HP :to pump :IP :and deliver gas to said pump. There the energy stored in the :gas ltrom 'tank HP :is utilized :to pump low :pressure .gas, supplied to pump IP from holderwLP through tconduits .2 and 7, through a conduit 15 at :an intermediate pressure to intermediate pressure distribution systems IPS..

The regulator R :controls the rate at which gas is summed .into the intermediate pressure system so that stile pressure :in said system .is'rnaintained at a proper value. The check valve VC'K may be incorporated in the pump IP as in the jet compressor hereinafter described :in connection with Fig. 12.

.A branch conduit 4:: (connects high pressure storage dank :10 conduit )5 and "the intermediate pressure distribution system l-PS through pressure regulating valve The valve VR is set to open at a pressure below ,tthcsmiliimum safe operating pressure of distribution systtern IRS and to close at a pressure at .or above the nor- .mal, desired pressure which is maintained in distribution system IPS by pump IP. Thus, in normaloperation valve NR remains closed.

The gas supplied by pump ,IP to distribution system IFS comprises a mixture of high pressure gas from holder HP and low pressure .gas from holder LP. Pump P is controlled manually or automatically at selected times to maintain thepgas in holder HP at a pressure substant-ially. higher than the discharge pressure of pump IP. Thusthemixture of ,gas comprises arelatively small proportion of high pressure gas and a relatively large pro portion of low pressure gas. If, because of a power failure or for any other reason, pump P ceases or is ceased to operate, pump IP continues operating at maximum tefiicieucy to maintain thedntermediate pressure for a substantial period of time, but the pressure in holder HP is diminished as gas is released from it to pump IP. As the pressure in holder HP is decreased,

the ratio, in the gas flowing through pump 1?, of gas from holder ,LP to gas from holder HP remains at a maximum for the corresponding nozzle pressure. Check valves in the individual compressor units of pump JIP or check valve VCK prevent gas from flowing through pump IP from distribution system IPS to vholder LP after the pressure in holder HP is reduced to a value below that required to assure pumping of the low pressure gas against the pressure in the intermediate pres sure distribution system.

Should the pumping rate of pump IP fail to meet the demand for gas in the intermediate pressure distribution system 'lPS, the pressure in conduit 5 would .fall below the desired, normal value. Regulating valve VrR would then open and. gas would be supplied to distribution system, IRS directly from holder .HP at .a pressure not lower than the minimum safe operating pressure of system IPS. t

In Fig. 2 the numeral .SdeSignates :a discharge manifold section supplying. a combustible mixture of gases to the intermediate pressure distribution system shown in Fig. 1, with conduit 6 arranged to supply high pressure gas to gas pumping units 8, 9, 10 and 11, for pumping low pressure gas from conduit 7 into conduit 5. A regulator 12 of well known form is associated with conduit 6 in a manner to maintain the pressure in the manifold 13, and consequently at the inlet ends of the respective shutoff valves 14, 15, 16 and 17, at a fixed value, which may be preselected by manual adjustment of knob 12a to vary the degree of spring loading of the diaphragm of regulator 12, indicated somewhat diagrammatically at 12b.

Valves 14 to 17 are normally closed by springs individual thereto, and go wide open when a preselected degree of fluid pressure is applied at the upper surfaces of their respective diaphragms. The operating means for the valve 14 is shown enlarged and in section, and diagrammatically, as comprising upper and lower fixed housing portions 14a and 14b, with a diaphragm 14c interposed therebetween; a valve rod 14d being suitably attached to-diaphragm. 14c, and a coiled spring li4e being interposed between the bottom wall of housing portion 14b and diaphragm 140 to normally bias the valve disk 14f against .its' seat to close the valve; said parts being shown, however, in valve-opening position. It is to be understood that the operating elements of valves 15, 16 and 17 may be of substantially the same size as the corresponding elements of valve 14, with the exception that the valve disks and their seats are preferably of sizes proportional to the sizes of the branch conduits in which they are respectively I located.

' gas which flows through conduit 7 preferably consists of low pressure gas and the enlarged inlet end 7a of conduit -'7 connected to low pressure holder LP may include a .sc'reen or other suitable form of filtering means (not shown).

The branch streams of high pressure gas flow through the jets 8a, 9a, 10:: and 11a of the respective units, which are provided with check valves 8b, 9b, 1% and 11b in the branch conduits 80, 9c, 10c and 110 through which the low pressure gas is supplied. The discharge of each ejector unit enters the discharge manifold and thence passes to the intermediate pressure distribution system. The low pressure gas duct 80, 9c, etc., of each ejector unit includesa manually adjustable throttling valve 8d, 9d, d and 11d, respectively. Gas enters the low pressure gas conduit or duct 7 through a throttling valve 18.

:Thegas pumping units 8 to 11, inclusive, are preferably of like construction, but difier in their respective sizes, as aforementioned; the sizes thereof being so selected that each unit has twice the pumping capacity of the next smaller unit. Thus, in a four-unit plant like that illustrated in Fig. 2, with the smallest unit 11 of predetermined ca pacity, the next larger unit 10 will have twice that capacity; the next larger unit 9 will have four times the capacity of unit 11, and the largest unit 8 will have eight times the capacity of unit 11. Accordingly, the units 8 to 11, inclusive, when active individually or jointly in various combinations, are adapted to'provide fifteen equal steps of increase or decrease in the pumping rate of the gas; each step corresponding to 6% percent of the total pumping capacity of the entire plant. The aforementioned throttling valve 18, which may be of the butterfly type, in the low pressure manifold 7 is operable automatically by a diaphragm motor 19, in the manner hereinafter described, to maintain substantially constant the difference between the values of the pressures within the low pressure manifold 7 and the aforementioned discharge manifold 5.

From the foregoing it will be apparent that the number of gas pumping units might be increased from four to five,

and again sized in geometrical progression; in which case thirty-one rates of gas pumping would be obtained, each increment in flow corresponding to 3.225 percent of the total pumping capacity of the entire plant.

An adjustable regulator 20 of well known form is adapted to control the pressure of compressed air supplied to conduit 21, one branch 22 of which communicates, through conduit 23 under given conditions, with the interior of pilot regulator 24, and through conduit 25 under given conditions, with the interior of pilot regulator 26. The other branch 27 of conduit 21 is adapted to communicate as shown with the four valve mechanisms 28, 29, 30 and 31. In practice I prefer to maintain the compressed air pressure in conduit 21 and in parts associated therewith at approximately twenty-five pounds per square inch. An air compressor is shown diagrammatically at 32.

The housings of valves 28, 29, 3t) and 31 communicate, through conduits 28a, 29a, 30a and 31a, with the dia phragrn motors associated with the aforementioned valves 17, 16, 15 and 14, respectively, to effect opening of one or more-of the latter under predetermined.conditions, against the normal spring bias thereof to closed position; the biasing spring of valve 14 being shown at 14c, as aforestated.

Pilot regulator 24 is adapted for operation in a manner to'control the action of a diaphragm motor 33 to effect step by step actuation of the rate scheduling mechanism designated in general bythe numeral 34, with consequent control of the aforementioned valves 28 to 31, inclusive.

The hydraulic stablizing means designated in general by numeral: 35, is adapted to modify the operation of pilot regulator 24 in a manner to prevent undesirable adjustments of the scheduling mechanism 34 and to prevent hunting.

Calorimetric control means (parts of which are shown at 36a and other parts of which are shown at 3611) are adapted to control the degree of spring loading on pilot regulator 26, through the medium of a reversible motor 37; the latter being operable automatically in the manner hereinafter described to maintain substantially constant ing that the air'pressure in conduit 38 (which affords communication between pilot regulator 24 and diaphragm motor 33) is at the desired value predetermined by the setting of pilot regulator 24. Under these conditions the not flow into the intermediate pressure distribution system is zeroand the distribution pressure will, of course, remain constant. 7

In the event of an increase in demand for the gas in the intermediate pressure distribution system corresponding to 3 percent of the maximum capacity of the plant; the net flow into the distribution system would be minus 3 percent, and the distribution pressure would decrease'at a rate depending upon the capacity of the distribution system and the maximum capacity of the plant. Saiddecrease in distribution pressure causes pilot regulator 24 to increase the degree of loading of diaphragm motor 33', which change in loading tends to and finally does (if unbalance of pilot regulator 24 continues long enough) cause a step'in the operationof mechanism 34 in a direc- 6 /3 percent of full plant capacity. Said increase in loading of diaphragm motor 33 also reacts through, the'medi um of hydraulic stabilizerbS to at least temporarily cf "feet a decrease in the .degree of .loadingrofpilot regulalator 24.

Hydraulic stabilizer 35 is preferably arranged or ad- "justed in a manner to exert a force on pilotregulator24 ,tribution systemof 3% ,percent of the total plantcapacity; that is to say, the difference between .the. increase in the rate of. gas pumping 6% percent) and theminus 3 percent of net flow incident .to the increase .of demand of 3 percent of the total plant capacity. Pilot regulator 24 therefore causesno appreciable movement of diaphragm motor 33 until thenet flow graduallybuilds up the distribution pressure to a value predetermined by .the

initial degree o-flo-ading of regulator z4iunatfectedby the action of hydraulic stabilizer 35.

Inasmuch as the position of the diaphragm 33a .oftdiaphragm motor 33 is substantiallydirectly-:related"to'the pressure maintained by pilot regulator 24, it;is, of course,

1 possible toincrease thedegree of .pressureoffiuid (from regulator 24) upon thebody of liquid in chamber 3312, as an incident to each given increase in the .rateof gas pumping, whilestill preventingexcessive hunting, by :in-

creasing the auxiliary loading effect produced by the hydraul1c stabilizer 35. The meansfor and manner for. at-

taining this result will be described in detail hereinafter.

It is to be understood thatundercertain conditions the rate of demand for gas may vary rapidly, sorthat the action of hydraulic stabilizer 35 may not have beendissipated by the time another step (increase .or decrease) in the rate of gas pumping becomes necessary. Therefore, two or even three, steps may be takenin quite rapid succession. The stabilizer 35 is therefore soconstructed and arranged that the effect thereof is limited to the equivalent of several steps, so that maximum temporary deviation from the desired control point cannot exceeda predetermined value.

If cup 65 is depressed about two steps the rise in liquid level outside of the cup is enough to make'the liquid spill over the top thereof. If cup 65 is raised about two steps the fallin liquidlevel outside of the cup is enough tofall below the bottom o-fcup 65; so that farther lifting of the cup causes nochange in the degreeof loading of regula- -.tor 24. It is obvious that upon high rates of demand from the intermediate pressure distribution :system, when the bucket 63 is high, more lifting and less depressing of .the

cup 65 than the aforementioned two steps would be'required for therelease to occur.

The aforementioned .calorimetric device, :although shownmore or less diagrammatically at 36a, 36b, is to be understood asincluding well known structural features and operative characteristics of each of the following patents, to which reference may he had for a more complete understanding of said device,namely: No. 1,625,277,

granted April 19, 1927, to Horace N. Packard; No.

2,002,279, granted May .21, 1935, to Edwin X. Schmidt; No. 2,415,913, granted February 18, 1947, to EdwinX. Schmidt; No. 965,824, granted July 26, 1910, to Morris E. Leeds, and No. 1,125,699, granted January 19 1915, to Morris E. Leeds.

Thus the portion 3.6a includes means for withdrawing, through conduit 36c, from distribution manifold 5, a continuous sample of the gaseous mixture, the total heating value per unit volume of which is continuously ascertained, and indicated at scale 36:! by a pointer 36e fixed to the shaft 56f. A cam member 36g attached to shaft 36f is operable to effect closure of the high direction contacts 3611, and a cam member 361' also attached to shaft 36 is operable to effect closure of the low direction contacts 361'. Also attached to shaft 36f is a cam memher 36k whichtcooper'ates with the various. elements l desigs nated in general by the numeral 361 for regulating. the part time on during which the heating. value adjusting motor 37 .may be operated in one direction or the other .to adjust the degree of loading of the pilotregulator 26. The elements36'l as shown include anelectric motor 36m connected with supply lines L1, L2,.for continuous operation thereof unidirectionally. The specified means for controlling operation of motor 37 .are substantially like those shown anddescribed in-PatentNo. 2,415,913 aforementioned, to which reference maybe had. YAs aforestated, the pilot regulator 26 is primarily responsive to variations in the pressure difference between the suction manifold '7 for the low pressure gasand'the pressure with in discharge manifold 5.

The pilot regulator 26 includes an assemblycomprising a pair of diaphragms 26c and 26), the central portions of which are backed by rigid metal plates, and the plates and diaphragms are attached in spaced relationship by a suitable number of rods or studs,..two or which are shown at 26g and 26h. The periphery of diaphragm 26e :is clamped between a lower housing member 26k andanin- .terrnediate housing member or ring 26i, a lower cham- .ber 26l being provided thereby. The peripherypf diaphragm 26 is clamped between ring 261 and the upper housing member 26 thus providing an intermediate chamber 26a and an upper chamber 26x. The aforementioned conduit25 extends through ring 26i in pressure-tight relationship .andterminates in a nozzle 260 with which an adjustable seat'mernber 26d is adapted .to cooperate to effect closure or opening of the nozzle or to permit a variable rate "of flow of compressed air through the latter. Cenduits 'dtl and dila afford communication between the aforementioned discharge manifolds and chamber 26lto subject diaphragm26e to the pressure of the intermediatepressure gas in manifold 5.

.A conduit 7b affords communication between the low pressure conduit 7 and the aforementioned chamber 26x, whereby the diaphragm 26f'is subjected to the de gree of pressure (or :partial vacuum) existing in conduit 7. Diaphragm 267 is normally subjected to the pressure of a coiled compressed spring 26m; the degree of compression of said spring being adjustable by an abutment 26m in the form of a traveling nut, whose position is varied upon rotation of a threaded shaft 260 in one direction or the other. Shaft 26o'is adapted to be driven, through gearing 26p and suitable speed-reducing gearing 26: by a split-field reversible motor 37, which is subject to control by the aforementioned means 36b operable by thecalorimeter-Ma.

The upper .surface of diaphragm 19a of diaphragm motor 19 is subjected to the pressure of fluid within chamber 26a through a medium of a conduit 1%; said pressure being adjustably vented to atmosphere by the means shown at 19c. Diaphragm 19a .is loaded for normal movement thereof in an upward direction (to effect-full opening of valve 18) by a spring 19d; suitable leverage 192 being interposed between diaphragm 19a and valve 13 for this purpose. By the means aforedescribed a pre selected normal differential value of the pressure conditions in conduits 5' and 7 is insured, thus .insuring maintenance of proportionality of the flows of high pressure gas and low pressure gas in the active gas pumping units. For the purpose of providing the desired proportionality, initial manual adjustment of valves 8a to 11, inclusive, is involved. That is to say, the valves 8d to 11d, inelusive, are adjusted to compensate for any minor variations in the inherentproportio-ning characteristics of the respective gas pumping units with respect to each other. The last mentioned normal differential value is automatically varied in accordance with an operation of calorimeter 36a to insure maintenance of. a predetermined constant total heating value per unit volume of the gaseous mixture supplied to the intermediate pressure distribution system through manifold 5.

.The operation of the step .by step mechanism 34 is as follows: The rateof'fiow of compressed air through conduits 22 and 23 into chamber 24a of pilot regulator 24 is controlled by movement of valve seat 24b relatively to valve nozzle 24c. Valve seat 241) is adjustably mounted, as by means of 'bolt 24d, upon the lower diaphragm 24s of the assembly including the upper diaphragm 241; the diaphragms 24a and 24) being rigidly attached to each other in spaced relationship by a multiplicity of posts, two of which are shown at 24g and 24/2. The peripheries of the diaphragms 24c and 24 are clamped between the ring 24 and the top and bottom housing members 241' and 24k; thus forming the aforementioned chamber 24a between diaphragms 24c and 24f, and the chambers 24] between the lower diaphragm 24c and housing 24k. Conduits 4t) and 39 afford communication between discharge manifold and chamber 241, so that the lower face of diaphragm Me is subjected to the degree of pressure existing in the intermediate pressure distribution system.

The effective areas of diaphragms 24c and 24f are substantially equal when the diaphragm assembly (2412, 241, 24g, 2411) is in the normal operating position, which is determined by the position of valve seat 2412 with respect to-said diaphragm assembly and the distance which must separate the valve nozzle 240 from valve seat 24b to satisfy the normal rate of flow out of chamber 24a. The distance just mentioned varies only to a very slight degree as an incident to variations in the degree of pressure in chamber 24a and such variations in distance do not appreciably aliect the effective areas of diaphragms 24c and 24 and therefore the forces exerted by the variable pressure on these diaphragms remain substantially equal and opposite, provided that normal operating positions are properly adjusted. Valve seat 24b is adjustably mounted in the diaphragm assembly, so that by raising or lowering the valve seat in the diaphragm assembly the normal operating position of the diaphragm assembly is either lowered or raised, changing the relative effective areas of the diaphragms. Raising the diaphragm assembly makes the relative effective area of the top diaphragm 24 larger than that of the lower diaphragm Me, so that an increase in loading pressure in chamber 24a, associated with increase in rate of gas pumping, exerts an upward force on the diaphragm assembly, and thus reduces the loading on the regulator 24. Thus by lowering valve seat 241') in the diaphragm assembly the control point of regulator 24 can be made to become lower as a function of the pressure in chamber 240, or regulator 24 can be made to depart from full floating type of control and give proportional control in which the controlled pressure is reduced as the maintained pressure in chamber 24a is increased. The stability of control inherent in proportional mode of control provided by this characteristic may in some instances be desirable, particularly in instances where exceedingly long time lags are involved in the system. Under any condition the departure from the control point corresponding to a single step of make will be small so that the control point of regulator 24 is substantially unaifected by the loading pressure in chamber 240.

Pilot air from chamber 24a passes through conduit 38 to the chamber 33b forming an oil pot, said chamber 33b being adjustably vented to a low pressure point, such as the atmosphere, through an adjustable orifice 38a. A reduced portion of conduit 330 is positioned between chamber 33b and the upper chamber 33d ofthe diaphragm motor 33; said reduced portion having therein an orifice 332 which alfords communication between said chambers 33b and 33d. Diaphragm 33a of motor 33 is biased upwardly by a coiled compression spring 33 Chambers 33d and 33b contain a sufiicient quantity of a suitable liquid, such as mineral oil, to insure the presence of some of the oil in chamber 33b even though diaphragm 33a is in its downward extreme position; and the chamber 33b is of a sufficiently large size to insure against rotation.

8 that oil will not be forced into conduit 38 when diaphragm 33a is in its-upper extreme position.

As the rate of flow of pilot air, into chamber 24a is permitted to increase the net flow into conduit 38 and chamber 33b increases, thus increasing the degree of air pressure. The increase in air pressure tends to slightly increase the degree of loading of pilot regulator 24, increases the rate of flow through the orifice or bleeder 38a and causes oil to flow from chamber 33!) through orifice 33c into chamber 33d, against the bias of spring 33 at the lower face of diaphragm 33a. As a result the connecting rod 41 is moved downwardly, thereby effecting movement of gear segment 42 in a counterclockwise direction about its pivot 43, which is carried by a fixed support 44. Segment 42 is continuously engaged with gear 45, which is formed integrally with or otherwise rigidly attached to both the latch gear 46 and the drive arm 47 (through the medium of hub member 48); the assembly of gears and 46, hub 48 and arm 47 being free to rotate relatively to shaft 49 under the conditions hereinafter described.

Shaft 49 is freely rotatable in fixed bearings at opposite ends thereof; one of said bearings being shown at 50. Mounted upon and rigidly attached to shaft 49 for rotation therewith are step gear 51, pulley or winding wheel 52, and cam members 53 and 5d. Step gear 51 has formed integrally therewith or otherwise rigidly attached thereto a pair of abutments 51a and 51b against which one head portion of each of a pair of studs 55 and 56 (held captive adjacent opposite ends of arm 47) are respectively adapted to abut under the bias afforded by the coiled compression springs 57 and 58, respectively. The arrangement is such that clockwise movement of drive arm 47 about shaft it and with respect to step gear 51 will compress spring 58, thus causing stud 56 to exert, through abutment 51b, a clockwise torque upon step gear 51. Stud 55 is simultaneously moved away from abutment 51a. A similar effect, in the reverse direction, is produced by a counterclockwise movement of drive arm 47.

Step latch 59a forming part of a compound lever 59, pivotally mounted upon a pin or rod 60 carried by a fixed bracket 61, is arranged to engage between a pair of the multiple teeth 510 of step gear 51 to lock the latter The arm 5% of lever 59 has pivoted thereto at 59 an actuating latch 5%. which is normally biased to an intermediate position (not shown) by a roller 62a which is rotatably supported at one end of a lever62, whose other end is pivotally supported at 62!) to a downward extension 5% of said arm 5%. The upward bias of roller 62a is afforded by a suitable coiled compression {spring 62c interposed between the lower edge of lever 62 and a fixed abutment 62d.

Actuating latch 55%! is arranged to engage between any adjacent pair of the multiple teeth 460 formed peripherally upon latch gear 46, in such a manner that clockwise rotation of gear 46 rotates latch 59d in a counterclockwise direction about pivot 590 until the right-hand lug 59f of latch 59d engages an abutment 59g carried by arm 5% aforementioned, thereby preventing further counterclockwise rotation of latch 59d with respect to arm 5%. Continued clockwise rotation of gear 46 will then force lever 59 to move in a counterclockwise direction about rod 60, thereby causing movement of latch 59a out of engagement with step gear 51. The shape of the teeth in step gear 51 and latch 59a are such that after latch 59a has been moved partly out of the notch between a pair of teeth, the torque exerted by spring 53 will be sufficient to act upon lever 59 to compress spring 62c to the required degree to permit latch 59a to clear the outer end of the particular cooperating tooth of step gear 51, and to also permit latch 5941 to clear the outer end of the particular cooperating tooth of latch gear 46; with consequent return of latch59d to its aforementioned ,Lintermediateposition; the same droppinginto thenext adjacent notch between a pair of the teeth on gear 46.

,It is to be understood that when step gear 51 is released the load exerted on stud 56, through spring 53, is-likewise released. Such unloading tends to make rod 41 of diaphragmmotordll move anadditional amount. Inasmuch as some time is required for lever 59 to drop latches 59d and Shainto the respective gears 56 andSl,

"orifice 33c and the aforementioned body of oil are provided. The sudden change iuthe degree of loading upon the ,lower face of diaphragm 33a would result in substantially instantaneous movement ofsaid diaphragm, ex-

eept for the fact-that any movement of diaphragm 33a immediatelyresults in the establishment of a pressure drop of high value through orifi e 33a, thus reducing the pressure upon the upper surface of diaphragm 33a and insuring a rate of movement sulficiently slow to prowheel 52,and cams 53 and 54 through a corresponding angle, with consequent operation of one or more of the valvev mechanisms 28 to 31, inclusive, in a manner to effect application of pressure to, or,rel,eas e.o'f pressure from, the upper surfaces or" certain of the operating diaphragmsof valves 14 to "i, inclusive (see diaphragm 1140),; which valves are normally spring-biased to their respective closed positions. With cams 553 and 54 inthe positions thereof shown in Fig. 1 gas pumping units 8, 9 and were in operation (step number 14). One fartherqstep of clockwise movementof gear 46 would result in a corresponding degree of angularmovement of cams 53 and 54, whereby units '8, '9 and would be maintained in operation and valve mechanism 28 would be permitted by cam '53 to operate tolbring'in the gas pump-- ing unit 11, thus providing for full capacity operation of the entire plant.

Said last mentioned step of gear 46 in a clockwise direction would also effect aproportional degree of lifting of abucket .63", which is suspendedby a belt or tape 'd'd-attached to wheel 52. Bucket 63 is partially filled to a predetermined level with a suitable liquid, such as mineral oil. A'cup 65 is so positionedwithin'bucket 633 that the normal level of the liquid will be betweenthe bottomwallandthe upper edge ofthe cup in any operative position of bucket 63. As shown, cup 65 is rigidly attached to a lever 66, which is pivoted at 660 to an extension of the pilot regulator '24. A slider 66b is mounted to slide upon a part of lever 6'6; said slider preferably including a roller 660, which is continuously engaged with a counter-lever 67', which is pivoted at 67a to another extension of pilot regulator 24.

A red '68, which ispreferaoly adjustable in length (as by means of the threadedlyconnected elements 68:: and 68b), is interposed between counter-lever 67 and the upper surface of the backing-plate of diaphragm 24 Rod 68is 'so adjusted in length that-with'the diaphragm assembly-in'its normal position counter-lever 6'7 and the portion of lever 66 carrying slider 6612 will besu'bstantially parallel "to each other, whereby -slider6db may be moved towardor farther away from pivot 66a, to change the degree ofamp'lification of the force exerted by cup 65 upon rod 68 without any required change in the relative position ,of cup .65.

Cup 65 and'lever as normally tend to jointly exert a elockwisetorque, with a resultant downward force upon the aforementioned assembly of diaphragmsjzdf and Me, which "is additional to the manually adjusted force ro: duced by spring 24m Astep of movementof wheel 52 r 1.0 in {the clockwise rdirectionraises bucket 63. and 1(through the medium of theliquid in the (latter) tends tollift cup 65, thus reducing the degree of force exerted by rod 68 upon the diaphragm assembly 24c and 24 .245 2411.

.Such movement or bucket 63 raises the level ,of'liquid in the annular space between bucket (93 and cup 65. The temporarily increased displacement of the liquid in bucket 63 by cup v65 determines the degree ,o'freduction .in the loading, of pilot regulator 24.

Cup 65 is provided with an orifice or opening 65a which provides for gradual equalization of the level of the liquid inside of cup 65 with respect to that outside thereof.

Suitable means is preferably provided for adjusting the size of orifice 65a so that the rate ofdecrease in auxiliary loading of regulator 24, as an incident to a step movement,.may,be readily adjusted in accordance with conditions in a given installation, in respect of capacity ofthe distribution system, increment in flow for each increase inthe rateof gas pumping, and provision of the desired distribution pressure. In Fig. 2 I have shown, .by way of example, an adjustable screw 65b 'for varying the size of orifice 65a.

Similarly, in the event of a step of movement of wheel 52 in a counterclockwise direction, the displacement of liquid by the cup 65, is decreased, thus increasing the degree of'force applied by rod ,68 to diaphragm assembly 24c, etc. the orificedb'a acting as aforedescribedto effect .gradual equalization of the level of theliquidins'ide the cup 65 with respect .to that outside thereof, as aforedescribed.

With respect to theeffect o'frnetllow (that is to say,.the rate of gas pumpingminus the rate of demand for the gas from the intermediatepressure distribution system upon the degree ofpressure of the gas inthe distribution system, I have'hereinabove pointed out that "the distribution pres .sure should preferably be increased at a rate substantially proportional to the increase ,inthe rate of demand, thus providing for proper determination of the most desirable rate of gas pumping.

With fifteen steps of Variations of equal value in the rate of gas pumping, as provided by the fifteen-step mechanism jhereinabove described, each step of increase or decrease in the rate of gas pumping represents ,a changein the rate ofgas pumping corresponding to SiX and two-thirds percent of the total capacity of'the plant.

It is therefore possible to set the rate of gas pumping bution system and the total plant capacity.

For example, with a distribution system having a volumetric capacity equal to one-half of the maximum hourly capacity of the plant, the change in rate of gas pumping corresponding to six and two-thirds percent of the maximum rate ,of gas pumping would be .133 percent of the capacity of the distribution system per hour. .In one'hour the distributionpressure would therefore change 13.3 percent of one atmosphere, or at a rate of: (.133) (408:), divided by 60, inches of water per minute; or, in general, with a distribution system'having a volume in cubic feet equal to Vd times the maximum hourly capacity of the plant in cubic feetper'hour, the maximum rate of net flow of 6 /3 percent of maximum-capacity will cause a changeinpressur'e at a rate of 0.453/Vd inches of water column per minute. The minimumrate of change would, of course, be zero, and injnormal operation of the system the rate'of change would vary between zero and the above mentioned maximum determined by the value of 'Vd, which as willbe understood maybe determined by dividing'the volumetric capacity of the distribution systemby the maximum volumetric capacity of the plant perhour. Theminimum rate of pressure change could, of course, bezero the net flow were zero, butit is to be under- 11 stood that in general the rate of gas pumping will seldom correspond exactly with the rate of demand. Therefore the pressure will usually be changing in one direction or the other.

It may also be noted that if the demand is steady at one percent of total plant capacity above one particular step of gas pumping, the plant will (in order to average a constant pressure) operate on this step (six and two-thirds percent minus one percent divided by six and two-thirds percent) or eighty-five percent of the time, and fifteen percent of the time on the next higher step. With the demand half-way between two steps or rates of gas pump ing the period of operation on each step above and below the desired value should be the same in order to maintain a constant average pressure.

The customary method of control of a multi-unit system of this general type utilizes a mode of control known as proportional-position-action control in which there is a continuous linear relationship between value of pressure and the rate of gas pumping. More specifically, for each successive decrease in pressure there is a definitely related increase in rate of gas pumping. Such a system inherently tends to be stable, but it also inherently tends to maintain a lower pressure as the rate of gas pumping increases. When associated with a step-by-step action such usual method also includes the additional disadvantage that the running time on any particular step is decreased.

Maintenance of a lower pressure as an incident to each increase in the rate of gas pumping is definitely objectionable in a distribution system, because the increased pressure drop from the gas mixing plant to the various different points of consumption (as an incident to the increased rate of demand) makes it very desirable to maintain a higher pressure at the plant as the demand increases. Such a system would, in general, be unstable and cause hunting; and an important phase of the present invention resides in the novel method of and means for preventing instability and excessive changing of the rate of gas pumping.

One suitable means for insuring the desired degree of increasein the distribution pressure (as represented by the degree of pressure in distribution manifold as an incident to an increase in the rate of demand for the gas, is illustrated in Fig. 2, and comprises a known form of cam member 69 having an operative low point 69a and an operative high point 6% with a cam surface 690, therebetween; said surface 69c being spaced radially outwardly from shaft 49 at a uniformly increasing rate from point 69a to point 69b. In practice the low and high points are angularly spaced only slightly less than 180 degrees from each other. Member 69 is keyed or otherwise nonrotatably attached to shaft 49 at such a rotary angle that when all of the units of the plant are inactive a portion of the cam surface 690 adjacent the high point 6% thereof will underlie a roller or similar member 70a rotatably supported by pin 70b upon a lever 70 pivotally supported at 70c upon a suitable fixed member 70d. A flexible wire or cord 71 has one end thereof attached to lever 70 adjacent the free end of the latter; the other ,end of-cord 71 being attached to the hooked upper end of a coiled tension spring 72, Whose lower end is attached to the aforementioned lever 66 carrying cup 65. Thus with the various elements of the system in their respective initial positions the degree of tension of spring 72 will be at a maximum, thereby reducing to, itsminimum normal value the degree of loading of regulator 24. As shaft 49 rotates step-by-step in a clockwise direction cam surface 69 will act to gradually decrease the tension of spring 72.

The condition wherein all of the gas pumping units 8 to 11 inclusive, are inactivemay occur when the system isemployed for peak shaving, or as a means for maintaining a desired distribution pressure where another or main supply of combustible gas may be insufiicient in quantity to satisfy the maximum possible demand. However, when. -a.system..like. that'discloseddn F ig Z is employed as the sole supply of combustible gas' to a distribution system, normally eitherr the smaller gas pumping unit 11 or any one of more of the units 8 to 11, inclusive, will be in operation at any given time, depending upon the instantaneous rate of demand as reflected by variations in the distribution pressure after each automatic setting, or resetting, of the parts of the system.

If it be assumed that all of the gas mixing units 8 to 11, inclusive, are inactive (as an incident to lack of demand for gas in the distribution system) the latch gear 46 will have been rotated in a counterclockwise direction to one of its extreme positions; the shaft 49 and cam members 53 and 54 being moved simultaneously therewith. Upon a drop in the distribution pressure the parts aforedescribed will act to initiate operation of the smallest gas pumping unit 11, thus supplying to manifold 5' a combustible gas at a volumetric rate corresponding to one-fifteenth of the maximum capacity of the entire system (step 1). If the demand is not satisfied unit 10 will be rendered active, and operation of unit 11 discontinued, thus doubling'the volume of gas supplied to the distribution system (step 2). Always assuming that the demand is not satisfied, the units will further be operated as follows: Unit 10 will be continued in operation and unit 11 will be actuated (step 3); unit 9 will then be actuated, and operation of units 10 and 11 discontinued (step 4); unit 9 will be continued in operation and unit 11 will be actuated (step 5); unit 9 will be continued in operation, actuation of unit 10 will be effected, and operation of unit 11 discontinued (step 6); units 9 and 10 will be continued in operation and unit 11 will be actuated (step 7); unit 8 will then be actuated and operation of units 9, 10 and 11 discontinued (step 8); unit 8 will be continued in operation and unit ll will be actuated (step 9); unit 8 will be continued in operation, unit 10 will be actuated, and operation of unit 11 discontinued (step 10); units 8 and 10 will be continued in operation, and actuation of unit 11 will be effected be continued in operation, and actuation of unit 11 effected (step 13); units 8 and 9 will be continued in operation, actuation of unit 10 effected, and operation of unit 11 discontinued (step 14, which is the condition of the system illustrated in Fig. l); and upon a further demand for gas units 8, 9 and 10 will be continued in operation, and actuation of unit 11 effected (step 15).

Cam members 53 and 54 are cooperatively shaped and arranged with respect to each other and to the pairs of valves 28, 30 and 29, 31 as to provide the aforedescribed sequence of operation of units 8 to 11, inclusive, as an incident to the aforedescribed step-bystep rotation of shaft 49 in a clockwise direction from one extreme position to the other. More particularly, valves 28, 29, 30 and 31 have rollers 28b, 29b, 30b and 31b, respectively, associated therewith for actuation by the various cam formations. Thus, with all of the units 8 to 11 inactive, the points 53a and 53b of the high portions of cam member 53 will respectively engage rollers 28b and 30b to effect closure of valves 17 and 15; and the points 54a and 54b of cam member 54 will respectively engage rollers 29b and 31b to effect closure of valves 16 and 14. Upon the first step of clockwise movement of shaft 49 (with corresponding movement of cam members 53 and 54) the cam depression or valley 530 will be alined with roller 28b, to permit downward movement of piston 280 to an extent sufficient to aflord communication between conduits 27 and 2811, thus effecting full opening movement of valve 17, to initiate operation of gas pumping unit 11. Under '13 t the conditions just mentioned the other pistons 29c, 3tlc and 31c will be retained in their inner extreme positions, whereby closure of the other valves 14, 15 and 16 is insured.

Upon the next step of clockwise movement of shaft 49 roller 2% will ride up onto the raised or hill portion 3d of cam 53, thus effecting movement ofwpiston 28c to its inner extreme position ,(like .the position thereof shown in Fig. 2) to interrupt communication between conduits 27 and 28a, and to vent the latter to atmosphere, thus providing for reclosure of valve 17 under its normal spring bias to discontinue operation of unit 11. At the same time the cam surface 541; will have moved out of alinement with roller 29!; and the latter will be freed to move into the next adjacent portion of the depression or valley 54c formed in .the periphery of cam member 54, thus permitting outward movement of piston 290 to afford communication between conduits 27 and 29a, thereby effecting full open positioning of valve 16, against its normal spring bias, to initiate operation of gas pumping unit 10. Under the conditions just mentioned the rollers 30b and 3112 will be engaged by the raised portions 53b and 54b of cams 53 and 54. With unit ill only in operation the distribution manifold 5 will be supplied with a volume of the gas corresponding to tWo-fifteenths of the maximum capacity of the system. in the next step of increase in the rate ofgas pumping the units and 11 will be operated jointly, to provide three-fifteenths of the total plant capacity; and in the next step of increase, operation of unit 9 will be effected and operation of units ill and M will be discontinued; and so on.

Ii the demand for the gas is or becomes of sufficient magnitude to require operation of all of the units 8 to 11, inclusive, jointly, the units will be operated automatically in the step-by-step manner aforedescribed; the calorimetric device having supervision of the proportionality of the constituents of the gaseous mixture supplied by each unit under all conditions, to insure maintenance of a constant desired total heating value per unit volume of thecombustible gas.

With reference to Fig. 2 it will be noted that the various elements of the system are in the respective positions thereof which provide for operation of the system at fourteen-fifteenths of its maximum capacity, units 8, 9 and 10 being in operation and unit 11 being inactive. Upon a predetermined degree of reduction of the pressure within the intermediate pressure distribution manifold 5, as an incident to a demand for the gas greater than that being supplied by the active units, the elements of the system will respond automatically to effect another step of rotation of shaft 49 in a clockwise direction, whereupon the depression or valley 53c in cam member 53 will be alined with roller 28b. As a result piston 280 will be free to move outwardly to afford communication between conduits 27 and 28a, with consequent operation of unit 11, as aforedescribed; the other units it, 9 and lid continuing in operation. The system will then be operating at its maximum capacity.

It will be apparent that most of the gas supplied to the intermediate pressure system IPS comes from holder LP rather than from holder HP. Thus, for a given amount of gas supplied to the intermediate pressure system lPS, a system which embodies the invention does not require that as much gas be pumped to high pressure, and in cases where such pumping is not or may not be continuous, does not require a high pressure holder of such large capacity as prior systems do. Also, inasmuch as less high pressure gas is released to the intermediate pressure distribution-system a pump P of smaller than usual size may be employed. Thus a substantially smaller capital investment is required to provide a system embodying the invention than is required to provide other systems of equal capacity.

'14 l claim:

1. ins system ioi distributing at low-pressure and :at intermediate pressure gas supplied atllow pressure, in combination, a gas source, a low pressure gas storage tankconnected to said source, a high pressure gas 'storage tank, a .conduitconnecting said low pressure tank to said high pressure tank, a compressor pump .in said conduit for compressing gas received from said .lowpressure tank and storing the same in said high pressure tank at high pressure, a low pressure distribution system connected to said low pressure tank for receiving gas and distributing the same at low pressure, an inter mediate pressure distribution system connected to both said low pressure tank and said high pressure tank for receiving gas therefrom, and means responsive to flow of gasirom said high pressure tank into said interme diate pressure distribution system for pumping low pressure gas from said low pressure tank into said intermediate pressure distribution system and maintaining the gas pressure in said intermediate pressure distribution system at a predetermined value, said means comprising a pumping device having a plurality of jet type cornpressors operating at maximum efiiciency and of sizes,

to afford a change in the rate t which gas is pumped into said intermediate pressure distribution system in the manner of a geometrical progression, a low pressure conduit having a check valve therein connecting said low pressure tank to said pumping device, a high pressure conduit connecting said high pressure tankv to said pumping device for supplying high pressure gas to operate said pumping device, an intermediate pressure conduit connecting said pumping device to said intermediate pressure distribution system for supplying gas at an intermediate pressure, regulating means responsive to variations in the pressure of the gas in said intermediate pressure distribution system from said predetermined value for rendering selected one of said jets operative dependent upon the direction of said pressure variations to maintain said predetermined value of gas pressure, a bypass conduit connecting said high pressure tank to said intermediate pressure distribution system for admitting high pressure gas directly to said intermediate pressure distribution system, and a normally closed regulating valve in said bypass conduit operable to open in response to variable downstream pressure for supplying gas from said high pressure tank into said intermediate pressure distribution system at a pressure not lower than said predetermined value when said pumping device is unable to maintain said predetermined value of pressure in said intermediate pressure distribution system.

2. In a system for distributing at an intermediate pressure gas supplied at low pressure, the combination with a gas source, a low pressure gas storage tank connected to said source and a high pressure gas storage tank connected to said low pressure tank, of a compressor pump between said tanks for compressing gas received from said low pressure tank and storing the same in said high pressure tank at high pressure, an intermediate pressure distribution system connected to said tanks, and means responsive to flow of gas from said high pressure tank into said distribution system for pumping low pressure gas from said low pressure tank into said distribution system and maintaining the gas pressure in said distribution system at a predetermined value, said means comprising a high-pressure-gas-responsive pumping device ,1 W16 predetermined ones of said jets active in accordance with References Citedin the file of this patent said pressure variations to maintain said predetermined UNITED STATES PATENTS value of gas pressure in said distribution system, a by- 2637 638 Schmidt 'May 5 1953 pass conduit connecting said high pressure tank directly to said distribution system, and a regulating valve in 5 2676876 Mosely 1954 said by-pass conduit operable to open in response to i down-stream pressure variations for supplying gas from OTHER REFERENCES said high pressure tank directly into said distribution Bulst et Gas Journal, 4634,

system at a predetermined pressure when said pumping 26, 1952, Pages device is inefiective to supply a sufficient quantity of 10 gas to maintain said predetermined pressure. 

1. IN A SYSTEM FOR DISTRIBUTING AT LOW PRESSURE AND AT INTERMEDIATE PRESSURE GAS SUPPLIED AT LOW PRESSURE, IN COMBINATION, A GAS SOURCE, A LOW PRESSURE GAS STORAGE TANK CONNECTED TO SAID SOURCE, A HIGH PRESSURE GAS STORAGE TANK, A CONDUIT CONNECTING SAID LOW PRESSURE TANK TO SAID HIGH PRESSURE TANK, A COMPRESSOR PUMP IN SAID CONDUIT FOR COMPRESSING GAS RECEIVED FROM SAID LOW PRESSURE TANK AND STORING THE SAME IN SAID HIGH PRESSURE TANK AT HIGH PRESSURE, A LOW PRESSURE DISTRIBUTION SYSTEM CONNECTED TO SAID LOW PRESSURE TANK FOR RECEIVING GAS AND DISTRIBUTING THE SAME AT LOW PRESSURE, AN INTERMEDIATE PRESSURE DISTRIBUTION SYSTEM CONNECTED TO BOTH SAID LOW PRESSURE TANK AND SAID HIGH PRESSURE TANK FOR RECEIVING GAS THEREFROM, AND MEANS RESPONSIVE TO FLOW OF GAS FROM SAID HIGH PRESSURE TANK INTO SAID INTERMEDIATE PRESSURE DISTRIBUTION SYSTEM FOR PUMPING LOW PRESSURE GAS FROM SAID LOW PRESSURE TANK INTO SAID INTERMEDIATE PRESSURE DISTRIBUTION SYSTEM AND MAINTAINING THE GAS PRESSURE IN SAID INTERMEDIATE PRESSURE DISTRIBUTION SYSTEM AT A PREDETERMINED VALUE, SAID MEANS COMPRISING A PUMPING DEVICE HAVING A PLURALITY OF JET TYPE COMPRESSORS OPERATING AT MAXIMUM EFFICIENCY AND OF SIZES TO AFFORD A CHANGE IN THE RATE AT WHICH GAS IS PUMPED INTO SAID INTERMEDIATE PRESSURE DISTRIBUTION SYSTEM IN THE MANNER OF A GEOMETRICAL PROGRESSION, A LOW PRESSURE CONDUIT HAVING A CHECK VALVE THEREIN CONNECTING SAID LOW PRESSURE TANK TO SAID PUMPING DEVICE, A HIGH PRESSURE CONDUIT CONNECTING SAID HIGH PRESSURE TANK TO SAID PUMPING DEVICE FOR SUPPLYING HIGH PRESSURE GAS TO OPERATE SAID PUMPING DEVICE, AN INTERMEDIATE PRESSURE CONDUIT CONNECTING SAID PUMPING DEVICE TO SAID INTERMEDIATE PRESSURE DISTRIBUTION SYSTEM FOR SUPPLYING GAS AT AN INTERMEDIATE PRESSURE, REGULATING MEANS RESPONSIVE TO VARIATIONS IN THE PRESSURE OF THE GAS IN SAID INTERMEDIATE PRESSURE DISTRIBUTION SYSTEM FROM SAID PREDETERMINED VALUE FOR RENDERING SELECTED ONE OF SAID JETS OPERATIVE DEPENDENT UPON THE DIRECTION OF SAID PRESSURE VARIATIONS TO MAINTAIN SAID PREDETERMINED VALUE OF GAS PRESSURE, A BY-PASS CONDUIT CONNECTING SAID HIGH PRESSURE TANK TO SAID INTERMEDIATE PRESSURE DISTRIBUTION SYSTEM FOR ADMITTING HIGH-PRESSURE GAS DIRECTLY TO SAID INTERMEDIATE PRESSURE DISTRIBUTION SYSTEM AND A NORMALLY CLOSED REGULATING VALVE IN SAID BY-PASS CONDUIT OPERABLE TO OPEN IN RESPONSE TO VARIABLE DOWNSTREAM PRESSURE FOR SUPPLYING GAS FROM SAID HIGH PRESSURE TANK INTO SAID INTERMEDIATE PRESSURE DISTRIBUTION SYSTEM AT A PRESSURE NOT LOWER THAN SAID PREDETERMINED VALUE WHEN SAID PUMPING DEVICE IS UNABLE TO MAINTAIN SAID PREDETERMINED VALUE OF PRESSURE IN SAID INTERMEDIATE PRESSURE DISTRIBUTION SYSTEM. 